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Full text of "Daldinia Vernicosa: A Pyroxylophilous Fungus"

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MYCOLOGIA 

Vol. X November, 191 8 No. 6 



DALDINIA VERNICOSA— A PYROXY- 
LOPHILOUS FUNGUS 

Arthur S. Rhoads 
(With Plate 14) 

The collector is thoroughly aware that numerous species of 
fungi occur prevailingly on burnt places. Although some of these 
forms are found elsewhere occasionally, many are so constantly 
associated with burnt places that they are sought only in such a 
habitat. In order to account for this peculiar association many 
plausible but inadequate reasons have been advanced. The fact 
remains, as stated by Seaver (i), that sterilization of the sub- 
stratum by heat apparently brings about some change in the soil 
other than the simple elimination of competition in the destruc- 
tion of bacteria and other fungi, which changes appear to be of 
vital importance in the cultivation of fungi which normally grow 
on a burnt substratum. Later experiments by Seaver and Clark 
(2), dealing with the artificial cultivation of a species of Pyro- 
nema, show that soil heated in various ways, especially by burning 
over the surface, becomes a very favorable nutrient medium for 
fungi of various kinds by reason of the large amount of food ma- 
terial rendered available through the heating of the materials in 
the soil. It is only natural to suppose that wood or bark, when 
burnt, likewise becomes a more favorable medium for the growth 
of certain fungi. 

The writer has made several collections of Daldinia vernicosa 
(Schw.) Ces. & De Not. in various states throughout the East and 
generally finds it to be associated with fire-scorched trees. So far 

[Mycologia for September (10: 231-275) was issued September 25, 1918.] 

277 



278 Mycologia 

as can be determined this fungus is confined entirely to dicotyle- 
donous trees but occurs upon a great number of species, prefer- 
ably upon fire-scorched trunks. It attacks small saplings even 
more readily than larger trees and seems to prefer species of 
hickory for a host. 

While making a survey of a burned area in the latter part of 
August, 19 16, with a view to securing data in regard to the 
rapidity of the deterioration of standing fire-killed timber by one 
of our most common sap-rotting fungi, the writer was impressed 
by the abundance of Daldinia vernicosa on the dead trees. An 
area was selected near State College, Pa., that had been burned 
for the first time, a surface fire having swept through it 1 year 
and 3 months previously. As a result the trees on this area, with 
few exceptions, were scorched so badly that they were killed out- 
right. From this burned area an average sample tract, 100 by 500 
feet, was laid off and the following data were secured for each 
standing tree within this tract: species, diameter (measured to 
the nearest inch) at breast height, conditions (as to whether dead 
or living), and the species of fungi growing upon it as evidenced 
by the sporophores upon the trunk. The species of trees upon 
this tract in the order of their importance were white oak, scarlet 
oak, white pine, mocker nut hickory, red maple, chestnut, and 
pitch pine. The data obtained are given below, the trees being 
tabulated by diameter under each species : 

Out of 71 scarlet oak trees upon this tract only 1 bore sporo- 
phores of Daldinia vernicosa. There also were present 15 red 
maples, 6 chestnuts, 2>7 white pines, and 1 pitch pine but no trees 
of these species bore sporophores. Out of a total of 363 dicotyle- 
donous trees occurring upon this tract 46, or 13 per cent., bore 
sporophores of Daldinia vernicosa within 1 year and 3 months 
after the trees were scorched by fire. All the trees tabulated 
above, save one, were dead at the time of the reconnaissance. 

The above figures clearly indicate how extensively and rapidly 
this ascomycete can propagate itself when afforded a favorable 
substratum. The accompanying photograph (Plate 14, A), taken 
in the latter part of August with a previous record of two months 
of dry weather, testifies to the luxuriant growth made by the 



Rhoads: Daldinia vernicosa 



279 



Summary of Trees Bearing Sporophores of Daldinia vernicosa by Species 

and Size 



Species 


1 
D.B.H. inches! No. of trees on 
| area 


No. bearing 
sporophores of 
D. vernicosa 


Per cent bear- 
ing sporophores 
of D. vernicosa 


QtitTCus alba 


2 

3 
4 
5 
6 

7 
8 
9 

10 

1 1 


12 

5i 
37 
40 
33 
27 
19 
8 

3 
6 


3 
16 

5 
5 
6 
1 






25 
31 
14 
12 




<< «t 


.1 


ti < t 


18 


<< 


4 



»< 1 1 


.. 





<< 





tt ti 











Quercus alba, total trees 


236 


36 


15 


Hicoria alba 


I 

2 

3 

4 
5 
6 
7 


7 

12 

6 

5 
3 

1 

1 


2 

4 
2 



1 


29 

33 

33 






ti 


«. 


ti tt 





., 





it tt 


100 




' 1 




Hicoria alba, total trees 




35 


9 


26 



sporophores of this fungus. Sporophores gathered and taken 
into the laboratory at this time shed copious quantities of spores. 

Associated with Daldinia vernicosa was another pyrenomycete, 
Nummitlaria Bulliardi Tul. The stroma of this fungus is effused, 
thin, and crustaceous. It overspreads the surface of the inner 
bark, throwing off the epidermis for 6 inches or more in extent 
and is black and carbonaceous at maturity. This fungus, how- 
ever, was found only on the white oak and scarlet oak trees. It is 
quite common throughout this region but always associated with 
dead oak trees. It is not, however, so restricted to fire-killed trees 
as is its associate, Daldinia vernicosa, but is apparently always 
associated with dead trees, preferably oak trees. 

The genus Daldinia is characterized by the peculiar structure of 
the stroma, which is superficial, subglobose, and has a black and 
carbonaceous external layer when mature, in which the perithecia 
are imbedded. The stroma is softer inside, of a radiate-fibrous 
structure and concentrically zoned. 

There are 24 species of Daldinia, mostly from the tropics, given 



280 Mycologia 

in Saccardo. For the most part they can be referred to Daldinia 
concentrica, which is a common and widely distributed plant oc- 
curring in almost every country in the world. In Australia this 
species assumes large size, frequently becoming two or three 
inches in diameter as it sometimes does in the western United 
States. In Europe, Daldinia durissima was proposed by Fries 
many years ago, but, according to Lloyd (3), no one else ever 
found it, a type at Kew being only the common D. concentrica. 
Massee found a specimen in tropical America (Trinidad) which 
he named Daldinia aspera. Lloyd, however, states that this spec- 
imen is not a Daldinia (3) at all but a Hypoxylon, probably H. 
cerebrinum (4). Leveille discovered two species in the United 
States, D. cingulata and D. loculata, but Lloyd (3) states that 
both are the common D. concentrica. Two well-known and ap- 
parently distinct species of Daldinia occur within the United 
States, namely D. concentrica (Bolt.) Ces. & De Not. and D. ver- 
nicosa (Schw.) Ces. & De Not. 

Peck (5), in his list of the plants of North Elba, reports Dal- 
dinia vernicosa on dead trunks of young, standing deciduous trees. 
He states that it is very doubtful if this and D. concentrica are 
really distinct species, and is of the opinion that connecting forms 
occur. It would appear that Peck had not collected Daldinia ver- 
nicosa as typified by the specimens in the Schweinitzian her- 
barium, for, if he had done so, it is difficult to see how such speci- 
mens could be considered identical with D. concentrica. 

The stroma of Daldinia concentrica is subglobose or hem- 
ispheric, or rarely obovoid, while that of D. vernicosa is sub- 
turbinate and sometimes contracted behind into a thick stipe-like 
base which is often concentrically wrinkled. The stromata of 
both species become black when mature, but that of D. vernicosa 
becomes distinctly shining. When young and immature the 
stroma of D. vernicosa contains a large quantity of a colorless 
gelatinous substance which dries down at maturity, forming the 
radiate-fibrous substance between the concentric zones. At ma- 
turity practically all of the substance between the thin, blackish, 
concentric zones under the terminal, monostichous perithecial 
layer is made up of a colorless, radiate-fibrous, dry-gelatinous 



Rhoads: Daldinia vernicosa 2&1 

substance. It is thus seen that the interior of the stroma of this 
plant is of a very heterogeneous texture. As a result of the loose 
texture of the radiate-fibrous inner substance the mature fruit- 
bodies can be crushed readily between the fingers. In Daldinia 
concentrica the interior of the stroma also is of a radiate-fibrous 
structure. Owing to its more homogeneous structure, however, it 
is fairly firm and solid, and specimens that have not been attacked 
by insects are very resistant to crushing. In the latter plant the 
radiate-fibrous substance is brown instead of colorless, as it is in 



d 



& 



CO 



Fig. i. Spores of Daldinia vernicosa showing various stages in the dehis- 
cence of the exospore wall after treatment with dilute KOH ; a, spore at time 
of shedding; b, spore showing the initial step in the dehiscence of the exo- 
spore wall ; c and d, spores showing the casting off of the exospore membrane ; 
e, cast-off exospore membranes, some with the valves still hinged together; /, 
a later stage of e, showing the return of the two valves to their original posi- 
tion. X 500. 

D. vernicosa (Plate 14, B), and the concentric zones are not so 
sharply defined as those of the latter species. As pointed out by 
Ellis and Everhart (6) the perithecia of D. concentrica are 
monostichous and not polystichous as stated by Saccardo. But 
little difference is exhibited by either the perithecia, asci, or spores 
of the respective species. The spores of D. concentrica are ob- 
liquely uniseriate with the ascus, inequilaterally elliptical, dark- 
brown, and finally opaque. They are somewhat variable in size 
but usually conform to 12. 5-18 n by 7-10 /x. The spores of D. 
vernicosa are about the same size as in the preceding species but 
are somewhat smaller and less variable in size. They usually con- 
form to the limits of 1 0-14.5 //, by 7-7.5 /*. 



282 Mycologia 

The spores of Daldinia vernicosa are peculiar in that, when 
mounted in dilute (5 per cent.) KOH or NaOH, the exospore 
wall, which is colorless, quickly dehisces and separates from the 
spore, which is dark-brown. A single peripheral line of dehiscence 
occurs at the center of the spore and the two halves of the exo- 
spore wall usually break away from one another as two valves, 
or they may dehisce partially and bend backward as if they were 
hinged, thus allowing the spore to free itself from its peripheral 
membrane (Fig. 1). The spores of Daldinia concentrica also ex- 
hibit the same behavior, and, with equal facility. These obser- 
vations on the dehiscence and shedding of the colorless exo- 
spore wall of these two species, when the spores have been 
mounted in dilute solutions of KOH and NaOH as well as certain 
other dilute alkaline solutions, have been confirmed by the careful 
and repeated examination of specimens from widely distant points 
in several localities. This dehiscence of the exospore wall is less 
evident, however, in old herbarium material. 

Ellis and Everhart (6) sum up the differences between Dal- 
dinia vernicosa and D. concentrica as follows: "This (D. verni- 
cosa) is distinguished from D. concentrica by its shining-black 
stroma, and the looser texture of the radiate-fibrous inner sub- 
stance which is cut by 8-12 dark-colored, membranaceous hori- 
zontal plates or layers. These are very noticeable in a vertical 
section even in the young plant, while it is still covered with the 
conidial layer and before the terminal, subglobose, ascigerous 
stroma has begun to appear. In the mature state, the fibrous inner 
substance and the horizontal membranes disappear to a greater 
or less extent, and leave the stroma more or less hollow, so that 
it may be easily crushed with the fingers, but in D. concentrica 
the inner substance remains firm and is also of a darker color. " 

Daldinia concentrica, according to Lindau (7), is of cosmo- 
politan occurrence on dicotyledonous wood, while D. vernicosa, 
according to Saccardo (8), is less widespread in its distribution. 
In addition, the latter species generally occurs on burned woody 
stems, whereas the former species does not seem to be pyroxylo- 
philous. 

It is often very difficult to secure mature specimens of D. con- 



Rhoads: Daldinia vernicosa 283 

centrica, and sometimes exceedingly difficult to secure mature 
specimens of D. vernicosa that are free from insects. Even after 
excellent specimens are collected, the interior portions of the 
stroma usually are eaten out by the larvae that hatch out within 
the specimens, unless they are quickly oven-dried. 

In addition to his own collections the writer has examined spec- 
imens of both plants in the herbaria of Dr. L. O. Overholts, The 
Pennsylvania State College, The New York State College of For- 
estry, Office of Pathological Collections in the U. S. Bureau of 
Plant Industry, the Schweinitzian herbarium in the Academy of 
Natural Sciences at Philadelphia, and the collections of the Office 
of Investigations in Forest Pathology. The Schweinitzian her- 
barium contains the type specimens of Daldinia vernicosa, which 
were first described as Sphaeria vernicosa by Schweinitz from 
specimens collected at Salem, North Carolina. 

Summary 

i. Daldinia vernicosa, as is typical of certain other fungi, oc- 
curs prevailingly on a substratum of burnt wood, and is to be re- 
garded as a pyroxylophilous fungus. 

2. In its occurrence, it apparently is confined to dicotyledonous 
species and attacks fire-killed saplings, particularly those of hick- 
ory, with great vigor. 

3. Out of a total of 363 dicotyledonous trees occurring upon 
an average sample tract ( 100 by 500 feet) of a burned area, 46, or 
13 per cent., bore sporophores of Daldinia vernicosa within 1 
year and 3 months after the trees were scorched by fire. 

4. Of the 24 (mostly tropical) species of Daldinia given in Sac- 
cardo, most of them can be considered as mere growth forms or 
ecological expressions of Daldinia concentrica, a widely distributed 
plant of cosmopolitan occurrence. 

5. Only two species of Daldinia occur in the United States, D. 
concentrica and D. vernicosa, which appear to be morphologically 
quite distinct. 

6. The dehiscence, of the colorless exospore wall occurs along 
a single central peripheral line and seems to be a characteristic 
feature of regular occurrence with the spores of both Daldinia 



284 Mycologia 

vernicosa and D. concentrica, when mounted in dilute alkaline 
solutions. 

Office of Investigations in Forest Pathology, 
Bureau of Plant Industry, 
Washington, D. C. 

Bibliography 

i. Seaver, Fred J. Studies in pyrophilous fungi — I. The occurrence and 
cultivation of Pyronema. Mycologia i: 131--139. pis. 9-12. 1909. 

2. Seaver, Fred J., and Clark, Ernest D. Studies in pyrophilous fungi — II. 

Changes brought about by the heating of soils and their relation to the 
growth of Pyronema and other fungi. Mycologia 2: 109-124. pis. 
24-26. 19 10. 

3. Lloyd, C. G. Daldinia vernicosa. In Mycological notes. No. 43, p. 604. 

1916. 

4. Lloyd, C. G. Hypoxylon cerebrinum. In Mycological notes. No. 42, p. 

579. 1916. 

5. Peck, C. H. Plants of North Elba, Essex Co., N. Y. New York State 

Museum Bui. 6: 67-266. 1899. (See p. 229.) 

6. Ellis, J. B., and Everhart, B. M. Daldinia vernicosa. In The North 

American Pyrenomycetes, p. 661. 1892. 

7. Lindau, G. Daldinia DeNot. In Engler and Prantl's Die natiirlichen 

Pflanzenfamilien. Teil I, Abteilung I, p. 487. 1897. 

8. Saccardo, P. A. Daldinia vernicosa. In Sylloge. Vol. i, p. 394. 1882. 

Explanation of Plate 14 

A. Trunk of white oak (Quercus alba L.) one year and three months after 
it was killed by a light surface fire, showing the abundance of Dalidinia verni- 
cosa. The trunk bears a 6-inch rule. 

B. Sporophores of Daldinia vernicosa, showing both external and sectional 
views, natural size. 



Mycologia 



Volume io, Plate 14 




A B 

DALDINIA VERNICOSA (Schw.) Ces. and De Not.